# DNS

List of DNS servers

* kuketz-blog
  * https://www.kuketz-blog.de/empfehlungsecke/#dns
* Digitalcourage
  * https://digitalcourage.de/support/zensurfreier-dns-server
  * DoT, DNSSEC: 5.9.164.112:853#dns3.digitalcourage.de
  * DoT, DNSSEC: 46.182.19.48:853#dns2.digitalcourage.de
* Digitale Gesellschaft
  * https://www.digitale-gesellschaft.ch/dns/
  * DoT, DNSSEC: 185.95.218.42:853#dns.digitale-gesellschaft.ch
  * DoT, DNSSEC: 185.95.218.43:853#dns.digitale-gesellschaft.ch
* UncensoredDNS
  * https://blog.uncensoreddns.org/dns-servers/
  * 89.233.43.71:853#unicast.uncensoreddns.org
* https://ffmuc.net/wiki/doku.php?id=knb:dohdot
  * 5.1.66.255:853#dot.ffmuc.net

## Unencrypted DNS - Network Manager Configuration

* https://wiki.archlinux.org/index.php/NetworkManager#Custom_DNS_servers

```shell
echo '[global-dns-domain-*]
# servers=serveripaddress1,serveripaddress2,serveripaddress3
servers=46.182.19.48,2a02:2970:1002::18,91.239.100.100,2001:67c:28a4::,89.233.43.71,2a01:3a0:53:53::' \
| sudo tee /etc/NetworkManager/conf.d/dns-servers.conf

sudo systemctl restart NetworkManager
```

## Encrypted DNS - systemd-resolved

* https://wiki.archlinux.org/index.php/Systemd-resolved#DNS_over_TLS
* https://www.freedesktop.org/software/systemd/man/resolved.conf.html#  
* `domains=~.`
    * https://unix.stackexchange.com/a/632292
* https://fedoramagazine.org/use-dns-over-tls/  

> systemd-resolved provides resolver services
> for Domain Name System (DNS) (including DNSSEC
> and DNS over TLS), Multicast DNS (mDNS) and
> Link-Local Multicast Name Resolution (LLMNR)

Installation:

```shell
# already preinstalled, contains systemd-resolved
sudo pacman -S --needed systemd

# remove openresolv! It is in conflict with systemd-resolvd
sudo pacman -Rns openresolv

# optional: install resolvconf replacement (for use with systemd-resolved)
sudo pacman -S --needed systemd-resolvconf
```

Resolver configuration:

```shell
sudo mkdir -p /etc/systemd/resolved.conf.d

echo \
'[Resolve]
DNS=5.9.164.112:853#dns3.digitalcourage.de 46.182.19.48:853#dns2.digitalcourage.de
DNSOverTLS=yes
DNSSEC=yes
FallbackDNS=185.95.218.42:853#dns.digitale-gesellschaft.ch 185.95.218.43:853#dns.digitale-gesellschaft.ch 89.233.43.71:853#unicast.uncensoreddns.org 5.1.66.255:853#dot.ffmuc.net
Domains=~.
Cache=yes
#LLMNR=yes
#MulticastDNS=yes
#DNSStubListener=yes
#ReadEtcHosts=yes' \
| sudo tee /etc/systemd/resolved.conf.d/DoT.conf >/dev/null
```

NetworkManager -> use systemd-resolved:

- There are multiple alternatives to do this
- From man page https://developer.gnome.org/NetworkManager/stable/NetworkManager.conf.html:
  If resolv.conf is symlink (see symlink
  line below), then NetworkManager wil automatically use
  resolvd. This is the nicest method.
    - https://wiki.archlinux.org/index.php/Systemd-resolved#DNS
- Alternative: Add "[main] <newLine> dns=systemd-resolved"
  to /etc/NetworkManager/conf.d/dns.conf
    - https://wiki.archlinux.org/index.php/NetworkManager#systemd-resolved

```shell
# resolv.conf generated by NetworkManager
sudo systemctl stop NetworkManager
if [ ! -f /etc/resolv.conf.backup ]; then sudo mv /etc/resolv.conf /etc/resolv.conf.backup; fi 
sudo ln -sf /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf
```

Enabling systemd-resolvd:

```shell
sudo systemctl enable --now systemd-resolved.service
```

Restarting NetworkManager:

```shell
sudo systemctl restart NetworkManager
```

After some seconds, `resolv.conf` should just contain `nameserver 127.0.0.53`

```shell
cat /etc/resolv.conf
```

## Troubleshooting

### View global and per-link DNS settings

```shell
resolvectl status
```

### Watch journal

1) Enable debug

```shell
sudo systemctl edit systemd-resolved
```
```
[Service]
Environment=SYSTEMD_LOG_LEVEL=debug
```

```shell
sudo systemctl restart systemd-resolved
```

2) View the log

```shell
journalctl -u systemd-resolved -f
```

## Verification of unencrypted DNS

```shell
sudo pacman -S --needed ngrep

sudo ngrep port 53
```

The destination IP addresses should be one of the configured dns servers:

```
yoda@yodaTux ~ % sudo ngrep port 53
interface: wlp1s0 (192.168.178.0/255.255.255.0)
filter: ( port 53 ) and ((ip || ip6) || (vlan && (ip || ip6)))
#
U 192.168.178.71:60481 -> 46.182.19.48:53 #1
  <............wiki.archlinux.org..... 
```

## Verification of unencrypted DNS

```shell
sudo pacman -S --needed ngrep

# output should be empty
sudo ngrep port 53

# configured DoT addresses should be visible
sudo ngrep port 853
```

```
yoda@yodaTux ~ % sudo ngrep port 853
[...]
#
T 192.168.178.71:48350 -> 5.9.164.112:853 [AP] #274
  ....P.G.B.(...%/. e"..A".w.>.h..a.../...<.3b.
  ^.d......'bj...w.qU.... ....90..4.LL.=.&
```
